1. Field of the Invention
The present invention relates to a method of and an apparatus for recording the duplicate color image of a color original on a color photosensitive material by exposing the color photosensitive material with a modulated beam. The beam is modulated in response to a color separation image signal which is generated by a computer in response to the photoelectrical scanning of the color original. More particularly, the present invention relates to a method of and an apparatus for recording the duplicate color image as a halftone dot image similar to a multicolor printed matter.
2. Description of the Prior Art
FIG. 1 shows a conventional apparatus for recording a color image on a color photosensitive material by scanning the color photosensitive material while exposing the same by a beam modulated in response to a color separation image signal. This apparatus is utilized for color proof in a multicolor printing, for example.
Referring to FIG. 1, an original drum 2 on which a color original 1 is attached and a recording drum 4 on which a color photosensitive material 3 is attached are coaxially or synchronously rotated by a motor 5, while a pickup head 6 and a exposure head 7 provided opposite to the original drum 2 and the recording drum 4, respectively, are moved along the respective axial directions of the drums 2 and 4.
The pickup head 6 has a well known function of color separation photoelectrical conversion, to output color separation image signals R, G and B of red, green and blue in response to the tone and density of the color original 1 at a scanning point. These color separation image signals R, G and B are received by a color arithmetic circuit 8 of a post-stage, which performs desired color correction and the like to convert the received color separation image signals R, G and B into other color separation image signals Y, M, C and K of yellow, magenta, cyan and black for use in forming color separation blocks The color arithmetic circuit 8 has a structure similar to that in a well known electronic color process scanner.
The color separation image signals Y, M, C and K are received by a color conversion circuit 9 which converts these signals Y, M, C and K into recording control color image signals y, m and c of yellow, magenta and cyan which contains the image recording of the color photosensitive material 3. These signals y, m and c are received by the exposure head 7 which comprises three light sources 10R, 10G and 10B for emitting red, green and blue beams, respectively, acousto-optical modulating elements (hereinafter referred to as AOMs) 11R, 11G and 11B placed on optical paths of the respective beams for modulating the respective beams and a mirror 12 and dichroic or half mirrors 13 and 14 for combining the three modulated beams from the AOMs 11R, 11G and 11B along a common optical path. The AOMs 11R, 11G and 11B modulate the red, green and blue beams in response to the signals c, m and y, respectively. The color photosensitive material 3 is scanned and exposed by the combined beam and thereby the duplicate color image of the original 1 is recorded on the color photosensitive material 3.
In general in an electronic color process scanner, color separation images are recorded on films on the basis of the color separation image signals Y, M, C and K, and thereafter machine plates or blocks corresponding to the color separation images are formed by using the films. These machine blocks are used for practical multicolor printing wherein images of the machine blocks are printed in a overlapped manner by using corresponding color inks. In general, color proof is performed prior to such process and printing steps. The color proof may be performed by using he above system for producing the duplicate color image of the original 1 recorded on the color photosensitive material 3. However, this system is not so suitable for the color proof, since it can produce only a continuous tone image while the image of practical multicolor printing system is a halftone dot image.